Method and combination for heating and dispensing hot melt materials

ABSTRACT

A method for heating and dispensing hot melt materials in which the hot melt material is contained in a tube having a cylindrical outer surface portion over a majority of its length, and the hot melt material in the tube is heated by a heater assembly through a heat transfer member having a cylindrical inner surface adapted to closely receive the cylindrical outer surface portion of the tube.

This is a division of application Ser. No. 07/216,798 filed July 8,1988, now U.S. Pat. No. 4,926,029.

TECHNICAL FIELD

The present invention relates to methods and combinations of structuresutilized in heating and dispensing thermoplastic or hot melt materials,and in particular methods and combinations of structures utilized inheating and dispensing hot melt adhesives (i.e., by thermoplastic or hotmelt materials we mean organic typically polymeric materials, includingbut not limited to adhesives, that are solids at normal roomtemperatures, will melt when heated to temperatures above roomtemperature, and will again solidify (and in the case of an adhesiveadhere to a substrate) when returned to room temperature.

DISCLOSURE OF INVENTION

The present invention provides a convenient method and combination ofstructures for heating and dispensing small amounts of hot melt materialsuch as the moisture curing hot melt adhesive described in copendingU.S. patent application No. 201,169 filed June 2, 1988, the contentwhereof is incorporated herein by reference. The hot melt material iscontained in a tube comprising a conformable metal hollow tubular wall,a closed second end, and an end wall having a central nozzle at a firstend of the tubular wall. The tubular wall and the end wall define acavity in which the hot melt material is contained, and the tubular wallhas a cylindrical outer surface portion over a majority of the axiallength of the tubular wall from its first end toward its second end. Thehot melt material is heated in the tube by a heater assembly comprisinga heat transfer member having a cylindrical inner surface adapted toclosely receive the cylindrical outer surface portion of the tubularwall, and means for applying heat to the outer surface of the heattransfer member to heat the hot melt material within the cavity to apredetermined temperature through the heat transfer member and the tube(e.g., a thermostatically controlled elongate electric heating elementcoiled around the outer surface of the heat transfer member).

Preferably the heater assembly includes a housing comprising a generallycylindrical portion having a base end adapted to be supported on ahorizontal surface with the axis of the cylindrical portion projectingvertically upward, the heat transfer member is mounted coaxially withinthe cylindrical portion of the housing and has an inlet end adjacent anupper end of the housing adapted to afford movement of the tube into andout of the heat transfer member with the end wall adjacent the base endof the cylindrical portion, and the housing further includes a coverportion adapted to releasably engage the upper end of the cylindricalportion of the housing over the closed second end of the tube receivedin the heat transfer member.

BRIEF DESCRIPTION OF DRAWING

The present invention will be further described with reference to theaccompanying drawing wherein like reference numerals refer to like partsin the several views, and wherein:

FIG. 1 is a sectional side view of a heater assembly containing a tubeof hot melt material included in the combination according to thepresent invention;

FIG. 2 is a top view of the heater assembly illustrated in FIG. 1 withthe tube and a cover portion of the heater assembly removed;

FIG. 3 is an enlarged fragmentary sectional view showing detail of athermostat included in the heater assembly of FIG. 1;

FIG. 4 is an enlarged fragmentary sectional view taken approximatelyalong line 4--4 of FIG. 3; and

FIGS. 5 through 7 are views, some of which are in section, thatsequentially illustrate forming the tube of hot melt materialillustrated in FIG. 1.

DETAILED DESCRIPTION

Referring now to the drawing, there is shown in FIGS. 1 through 4 aheater assembly 10 in which is positioned a tube 11 of hot meltmaterial, both according to the present invention.

Generally the tube 11 comprises a conformable metal (e.g., aluminum)hollow tubular wall 12 having an axis, a second end 13 closed by foldingand crimping an end portion of the tubular wall upon itself, and atapered end wall 14 at a first end of the tubular wall 12, which endwall 14 has a central nozzle closed by a threadably attached cap 16. Thetubular wall 12 and the end wall 14 define a cavity containing the hotmelt material, and the tubular wall 12 has a cylindrical outer surfaceportion 18 over a majority of the axial length of the tubular wall 12from its first end toward its second end (e.g., over half of that axiallength and preferably at least 70 percent of that axial length). Theheater assembly 10 for the tube 11 and hot melt material comprises ahousing 20 of thermally insulating polymeric material, a hollowcylindrical metal (e.g., aluminum) heat transfer member 22 mountedwithin the housing 20 having a cylindrical inner surface 24 adapted toclosely receive the cylindrical outer surface portion 18 of the tubularwall 12, and means for applying heat to an outer 26 surface of the heattransfer member 22 to heat the hot melt material within the cavity inthe tube 11 to a predetermined temperature through the heat transfermember 22 and the tube 11.

As illustrated, the housing 20 comprises a generally hollow cylindricalportion 28 having a base end engaged with a circular base portion 30 sothat by the base portion 30 the cylindrical portion 28 is adapted to besupported on a horizontal surface with an axis of the cylindricalportion 28 projecting vertically upward. The heat transfer member 22 ismounted coaxially within the cylindrical portion 28 of the housing 20 byhaving a lower end received in a socket in the base portion 30 and aninlet end adjacent an upper end 32 of the housing 20 received in astepped opening through an upper circular support portion 34 of thehousing 20 to afford movement of the tube 11 into the heat transfermember 22 to a fully engaged position shown in FIG. 1 with the end wall14 of the tube 11 adjacent the base end of the cylindrical portion 28,the cap 16 resting on the base portion 30 with a central tip on the cap16 projecting through a central opening therein, and the cylindricalouter surface portion 18 of the tubular wall in essentially full lengthengagement with the cylindrical inner surface 24 of the heat transfermember 22. The housing 20 further includes a cover portion 36 having athreaded lip 37 adapted to releasably engage mating threads adjacent theupper end 32 of the cylindrical portion 28 of the housing 20 over theclosed second end 13 of the tube 11 received in the heat transfer member22.

The means for applying heat to the outer surface 26 of the heat transfermember 22 to heat the hot melt material within the tube 11 to apredetermined temperature comprises an elongate rope like heatingelement 38 (e.g., a 250 watt 60 inch long heater) coiled around theouter surface 26 of the heat transfer member 22 and held in place by anoverwrap of pressure sensitive adhesive coated tape 40 (e.g., glasselectrical tape No. 69 available from Minnesota Mining and ManufacturingCompany, St. Paul, Minn.), and a temperature controlling thermostat 42connected in series with the heating element 38 and adhered in a slotalong a metal (e.g., aluminum) contact shoe 44 between the coiledheating element 38 and the heat transfer member 22. Electrical power isapplied to the heating element 38 through a conventional power cord 46and a thermal cut out 48 which will open at a predetermined hightemperature to prevents overheating of the system.

A method for forming the tube 11 containing hot melt material isillustrated in FIGS. 5 through 7. Generally that method comprisesproviding the tube 11 with its tubular wall 12 cylindrical along itsentire length and its second end 13 open as is illustrated in FIG. 5(which is a conventional shape for an unfilled tube); melting andpouring hot melt material 50 into the open second end 13 of the tube 11;folding and crimping closed the second end 13 of the tube 11 to theshape illustrated in FIG. 6; cooling the hot melt material filled andcrimped tube 11 as is illustrated in FIG. 7; and supporting thecylindrical outer surface portion 18 of the wall 12 to be sure itretains its cylindrical shape during the pouring, crimping and coolingsteps. Such support for the cylindrical outer surface portion 18 of thetube 11 during those steps (which is particularly needed during thecrimping step) can be provided by a cylindrical surfaces 52 defining abore in a block 54 (e.g., of aluminum), which surface 52 insures thatthe outer surface portion 18 of the tube remains cylindrical to duringthose steps to subsequently insure a close fit between the cylindricalouter surface portion 18 of the tube 11 and the inner surface 24 of theheat transfer member 22 and thereby insure good heat transfertherebetween. As can be seen in FIG. 7, the cooling step can beperformed by placing a plurality of the blocks 54 containing filled andcrimped tubes 11 in a liquid filled cooling tank 56 in which the liquidis stirred by an agitator 58 and a maximum liquid level below the upperends of the blocks 54 is assured by an open topped stand pipe 60.

To apply the hot melt material from the hot melt material filled tube11, the tube 11 is first positioned in the heater assembly 10 with itscylindrical outer surface portion 18 in contact with the inner surface24 of the heat transfer member 22 and the cover portion 36 is attachedto the rest of the housing 20 as is illustrated in FIG. 1. Electricalpower is applied to the heating element 38 to heat the material in thetube 11 primarily by conduction through the heat transfer member 22 andthe tube 11. After an appropriate time to thoroughly heat the materialin the tube 11 (e.g., 15 minutes), the cover portion 36 is removed, thetube 11 is withdrawn from the heater assembly 10, the cap 36 of the tube11 is removed, and the heated liquid hot melt material is extruded fromthe tube 11 by pressing opposite sides of the wall 12 together.

The present invention has now been described with reference to oneembodiment thereof. It will be apparent to those skilled in the art thatmany changes can be made in the embodiment described without departingfrom the scope of the present invention. Thus the scope of the presentinvention should not be limited to the structures described in thisapplication, but only by structures described by the language of theclaims and the equivalents of those structures.

I claim:
 1. A method for heating and dispensing hot melt materialincluding:containing the hot melt material in a tube comprising aconformable metal hollow tubular wall having an axis, a closed secondend, and a first end, and an end wall having a central nozzle closed bya removable cap at the first end of the tubular wall, the tubular walland the end wall defining a cavity in which the hot melt material iscontained, and the tubular wall having a cylindrical outer surfaceportion over a majority of the axial length of the tubular wall from thefirst end toward the second end; providing a heat transfer member havingan outer surface and a cylindrical inner surface having an axis andadapted to closely receive the cylindrical outer surface portion of thetubular wall; positioning the cylindrical outer surface portion of thetubular wall within the heat transfer member along its cylindrical innersurface; applying heat to the outer surface of the heat transfer memberto heat the hot melt material within the cavity to a predeterminedtemperature through the heat transfer member and the tube; removing thecap from the nozzle; and pressing opposite sides of the conformabletubular wall together to extrude the heated liquid hot melt materialfrom the tube through the nozzle.
 2. A method according to claim 1wherein said step of containing the hot melt material in the tubecomprises providing the tube with its tubular wall cylindrical along itsentire length and its second end open;melting and pouring the hot meltmaterial into the open end of the tube; crimping closed the second endof the tube; cooling the hot melt material filled and crimped tube; andsupporting the outer surface of the tube to retain the portion of theouter surface of the tube in the cylindrical shape over the majority ofthe axial length of the tubular wall from the first end toward thesecond end during the crimping and cooling steps.
 3. A method forheating hot melt material to be dispensed including:containing the hotmelt material in a tube comprising a conformable metal hollow tubularwall having an axis, a closed second end, and a first end, and an endwall having a central nozzle at the first end of the tubular wall, thetubular wall and the end wall defining a cavity in which the hot meltmaterial is contained, and the tubular wall having a cylindrical outersurface portion over a majority of the axial length of the tubular wallfrom the first end toward the second end; providing a heat transfermember having an outer surface and a cylindrical inner surface having anaxis and adapted to closely receive the cylindrical outer surfaceportion of the tubular wall; positioning the cylindrical outer surfaceportion of the tubular wall within the heat transfer member along itscylindrical inner surface; and applying heat to the outer surface of theheat transfer member to heat the hot melt material within the cavity toa predetermined temperature through the heat transfer member and thetube; said step of containing the hot melt material in the tubecomprising the steps ofproviding the tube with its tubular wallcylindrical along its entire length and its second end open; melting andpouring the hot melt material into the open end of the tube; crimpingclosed the second end of the tube; cooling the hot melt material filledand crimped tube; and supporting the outer surface of the tube to retainthe portion of the outer surface of the tube in the cylindrical shapeover the majority of the axial length of the tubular wall from the firstend toward the second end during the crimping and cooling steps.